This application pertains to the art of baking apparatus and more particularly to portable apparatus for baking pretzel-like bakery products in a continuous process. The invention is specifically applicable to baking pretzels in an oven having a chamber containing a number of processing stations wherein the bakery products are transported to the plurality of stations via a positively driven endless drive chain and will be described with particular reference thereto. Currently, popular automatic baking apparatus include a plurality of baking racks connected to drive chains for processing soft pretzels by first spraying the pretzels with a soda solution, salting the pretzels and then baking and browning the salted pretzels through use of radiant heat rods before the products are removed from the baking racks. It will be appreciated, though, that the present invention has broader applications such as conveyor belt baking operations wherein a plurality of baking stations are linearally traversed by means of a conveyor or the like in a oven-like chamber containing a number of sequentially arranged processing stations.
A fairly popular automatic baking apparatus is described in U.S. Pat. No. 3,935,807. That apparatus is illustrated in FIG. 1. According to that teaching, a housing is provided which includes an oven-like chamber therein, the chamber having a pair of power-driven belts which comprise a pair of endless drive chains 14 and 16. Baking racks 12 are pivotally connected to the pair of endless drive chains 14 and 16 in a manner to permit them to freely swing or pivot throughout the processing of the pretzels. The endless drive chains 14 and 16 are driven by a combination of a motor 18 and gearing in a gearbox 40 moving the baking racks at a controlled rate through a series of processing stations. The pair of endless drive chains 14 and 16 are supported on the housing through a plurality of free turning gears 36, 37, 38 and 39 which are mounted on rods supported by a portion of a frame 30 adjacent a side panel 32. These free turning gears include Teflon bearings to minimize gear drag.
Well known shortcomings of the above arrangements include premature failure of the Teflon drive chain bearings due to excessive heat buildup and premature wear on the bearings in the motor 18 due to side-loading on the motor output shaft.
With continued reference to the prior art pretzel oven of FIG. 1, the upper portion thereof includes a salter 22 which includes a closed cylinder 22a with a single longitudinal row of openings 72 located therein, allowing the salt contained within the cylinder 22a to fall out during rotation onto pretzels. Similar to the free turning gears 36, 37, 38 and 39 mentioned above, the rotating salt box of the prior art was supported by two Teflon saddles, which tended to soften at cooking temperatures, therefore deteriorated rapidly and failed in use.
Also, in the upper portion of the oven itself, a plurality of heating elements comprising five longitudinal Cal rods 24 provided sufficient quantity of heat to bake the frozen pretzel products as they progress through the oven supported on the baking racks. In addition to the Cal rods, five transverse infra-red quartz rods 28, in combination with individual reflectors 29, were provided to bake the upper portion of the pretzels and aid in imparting to the upper surface of the pretzels a unique light brown color that adds considerably to the appeal of the pretzels. Unfortunately, the arrangement of Cal rods and quartz rods provided inadequate control over the baking process itself to the extent that the exact cooking temperature of the oven could not be determined or readily controlled during operation. In practice, only a "setting" temperature was available to the operator. Thus, the set point temperature was unreliable and prevented diagnosis of pretzel quality problems. For example, a determination of whether light pretzels were due to failures in heating elements or whether they were due to defects in the pretzels themselves was not determinable. Some of the above problems in the baking process, though primarily attributable to the Cal rods and quartz rods, were also in part due to inadequate or improper insulation of the housing forming the pretzel oven.
In order to control the prior art oven, a mechanical thermostat was typically connected between a source of power and the Cal and quartz rods. This thermostat was usually of the bi-metallic type and thus imparted a substantial desensitizing effect to the temperature control which was due to slow response time, resulting in undercooked pretzels when the oven was fully loaded and dark blistered pretzels on the last rack in a series of a full load.
Maintenance costs of the prior art pretzel oven apparatus were quite high since the quartz rods, used as critical heating elements, were difficult to maintain. In use, the quartz rods have a life expectancy on the order of 2000 hours. Further, the wire leads feeding to the quartz rods were oftentimes unable to withstand the high temperatures which were periodically generated at the top portion of the oven. Both hardware and labor costs detracted from the profitability of operating such a pretzel oven apparatus according to the prior art.
With continued reference to FIG. 1, a common problem experienced in automatic pretzel ovens in the past has been a weakening of the one molar sodium hydroxide solution used for glazing through the spray tube 20 of the spray section at the bottom of the oven as salt from the salter 22 eventually migrated through the oven and into the catch tray 62. More particularly, salt not adhering to the pretzels themselves found no other place to go but into the catch tray 62 to mixedly combine with the sodium hydroxide solution weakening its effectiveness.
More serious shortcomings of the prior art pretzel oven includes a failure to detect fires within the oven itself. Should an oven of this type be left unattended for prolonged periods, a fire could start in the upper portion of the oven and continue undetected endangering both personnel and equipment.
It has, therefore, been deemed desirable to provide a safe, economical and improved continuous process pretzel oven.